The typical personal computing system employs a central processing unit, a video controller, and a video display device. The central processing unit provides address, data, and clock information to the video controller which interacts with the system memory to ultimately control the images displayed by the video display device.
Traditionally, personal computing systems have used cathode ray tube (CRT) type display devices. More recently however many manufacturers and vendors have employed flat panel display devices because flat panel devices have certain advantages over CRT's. For example, flat panel displays are lightweight and can be fabricated more compactly than can CRT devices.
The availability of both CRT and flat panel display devices has created several problems for manufacturers of personal computing systems and video controllers. Many of these problems stem from an essential difference between the flat panel display and the CRT display: the flat panel display has a slower response time and other limiting display characteristics because it is a chemically operative system. In contrast, the CRT is an electrically operative system. As one example, a CRT display is amenable to any number of horizontal and vertical lines of display, whereas the typical flat panel display can only handle a set number of vertical and horizontal display lines. On the other hand in order to keep down costs and proliferation of models and hardware, manufacturers of processor systems and controllers prefer not to design a different processor and video graphics controller to cover each CRT and flat panel display which may be included in a vendor's product line. It is similarly undesirable to reconfigure or recompute information during normal processing because a different display device is being used in the system.
Thus there exists a need for a system and method for driving both a CRT and flat panel display without involving a significant proliferation of hardware or disruption to normal processing.
Prior art patents known to applicant neither teach nor suggest any method or system for resolving the forgoing problems. U.S. Pat. No. 4,121,283 describes a display having a standard television type screen. The resolution is very low and the disclosure describes storing an image in memory in coded form and then displaying the image with real time decoding.
U.S. Pat. No. 4,399,435 describes a dual buffered alphanumeric system. A method of accessing memory in the blank intervals between two rows on the screen is disclosed.
U.S. Pat. No. 4,746,981 describes a method for sampling the video output from a television type display controller, and then expanding the image to fit a smaller portion of the image on an entire screen. This invention operates in an "interlaced" environment, does not teach or suggest a programmable or intelligent method for stretching an image, appears limited to an interlaced environment, and requires capture of the video output.